Delay line glass

ABSTRACT

A SILICA-ALKALI-METAL OXIDE GLASS COMPOSITION FOR USE IN PRECISION ULTRASONIC DELAY LINES. BY ADDING FE2O3 AS A SIGNIFICANT CONSITUTUENT, A RELATIVELY HIGH ALKALI-METAL OXIDE CONTENT CAN BE USED WITHOUT DEGRADING ACOUSTIC PERFORMANCE RESULTING IN LOWER TEMPERATURES BEING NECESSARY TO PRODUCE A HOMOGENOUS GLASS.

United States Patent 3,669,697 DELAY LINE GLASS Cyril Francis Drake, Harlow, and Robert Walter James Amos, New Barnet, England, assignors to International Standard Electric Corporation, New York, N.Y. No Drawing. Filed May 28, 1970, Ser. No. 41,570 Int. Cl. C03c 3/04, 3/10 US. Cl. 106-53 2 Claims ABSTRACT OF THE DISCLOSURE A silica/alkali-metal oxide glass composition for use in precision ultrasonic delay lines. By adding Fe O as a significant constitutent, a relatively high alkali-metal oxide content can be used without degrading acoustic performance resulting in lower temperatures being necessary to produce a homogenous glass.

BACKGROUND OF THE INVENTION This invention relates to a glass having a composition such that it has suitable properties for use as the delay medium in ultrasonic delay lines for color television, for computer stores, and for other applications requiring precision ultrasonic delay lines.

These suitable properties are a temperature coefiicient of delay for the transmission of ultrasonic sound waves in the MHz. range which is essentially independent of temperature parts per million per C.) in the temperature range 0-70 C., and an absolute value of delay which does not change with time.

It is known that glasses consisting of K 0, PbO, Si0 with some minor additions of other metal oxides have suitable properties for use as an ultrasonic delay line medium. One of the difiiculties in producing these known glasses is their low alkali-metal oxide content which results in very high temperatures 1600 C.) being necessary to produce a homogenous glass from the raw materials.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a glass having a composition including Fe O as a significant constituent together with silica and alkali-metal oxide.

More particularly the invention provides a glass having a composition comprising Mole percent (a) sio, 62.25-75 (b) PbO+BaO 10 20 With the BaO 0-(20% of the PbO) (c) Fe O 2.5-7.5 (d) M 0 2.5-7.5

where M 0 is any combination of alkali-metal oxides and at least three quarters of the total alkali-metal oxide is a single alkali-metal oxide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS By using Fe 0 as one of the significant constituents of a silica/alkali-metal oxide glass, a relatively high alkalimetal oxide content can be used, without degrading the acoustic performance.

Moreover the presence of Fe 0 makes it possible to reduce the PhD content without degrading the acoustic performance.

The constituents and their respective ranges of the glass of the present invention are selected from the following:

3,669,697 Patented June 13, 1972 ice where M 0 is any combination of alkali-metal oxides and at least three quarters of the total alkali-metal oxide is a single alkali-metal oxide.

Any one, some or all of the A1 0 Sb O and Bi O may be omitted, and replacement or partial replacement of one oxide by another of a type obviously similar to those skilled in the art art not to be excluded (for example the partial substitution, of up to about 20%, of PhD by BaO, e.g. substitution of 3 mole percent of PbO by 3 mole percent of BaO) as long as the SiO and (Fe O +M O) are substantially in the ratio defined by the range given above.

As an example, a typical glass composition is as follows:

The glass is manufactured by melting the mixed constituents in a refractory, e.g. alumina or fireclay, crucible in an oxidizing atmosphere, the melt temperature being of the order of 1500 C., casting or otherwise shaping from the melt into 'a suitable shape or shapes, and cooling from 600 C. to less than 50 C, at a substantially uniform rate over a period of not less than twelve hours.

An ultrasonic delay line having a delay medium comprising a block of glass having the composition as above and manufactured as described, had a temperature co efficient of delay for an acoustic signal of 5 MHz. through the length of the block of less than 3 parts per million per C. over a temperature range of 1070 C.

We claim:

1. A glass composition consisting essentially of Mole percent where M 0 is any combination of alkali-metal oxides and at least three quarters of the total alkali-metal oxide is a single alkali-metal oxide.

2. A glass composition, consisting essentially of:

Mole percent SiO 69.10 PbO 17.25 K 0 6.80 F6303 References Cited UNITED STATES PATENTS 2,562,292 7/1951 Black et al 106 53 3,326,702 6/ 1967 Babcock 106-53 3,517,345 6/1970 Krause 333-30 TOBIAS E LEVOW, Primary Examiner M. L. BELL, Assistant Examiner 

